The present invention relates to a method for determining timing differences between radio transmitters and a radio network incorporating the same. More specifically, the present invention relates to the determination of timing differences between base transceiver stations in a mobile radio network. This method of determining the real time differences is based on the measurement of the observed time differences.
In mobile radio networks such as the GSM system used throughout Europe, it is necessary that the position of each mobile station is known to the base stations with a sufficient accuracy.
There are already some methods for determining the locations of mobile stations in a mobile radio network. For many of the location methods such as those based on Time Difference on Arrival (TDOA) or Direction Finding (DF), it is necessary that the base transceiver stations operate synchronously with respect to each other. However, in the GSM mobile radio network as it is currently used in Europe, the base transceiver stations operate asynchronously with respect to each other, or the synchronisation is not accurate enough for location purposes. For this reason, it would be desirable to know the timing differences of the signals transmitted by the base transceiver stations.
However, no method is available at present which would be able to determine these timing differences. As a result, it is not possible to locate a particular mobile station with a high accuracy.
It is, therefore, an object of the present invention to provide a method for determining timing differences between a plurality of radio transmitters in a radio network. It is another object of the present invention to provide a method for determining timing differences between a plurality of base transceiver stations in a mobile radio network which would allow to increase the accuracy of locating the mobile stations. It is a further object of the present invention to provide a radio network in which such methods can be carried out.
According to the present invention, this object is accomplished by a method for determining timing differences between a plurality of radio transmitters in a radio network, comprising the steps of determining timing information of signals received by measuring means from said plurality of radio transmitters, and determining the timing differences between said plurality of radio transmitters on the basis of said timing information determined by said measuring means and the respective distance differences between said plurality of radio transmitters and said measuring means.
According to the present invention, this object is also achieved by a radio network as defined in claim 9.
In this way, the timing differences between the plurality of radio transmitters can be determined. Thus, if the radio transmitters are base transceiver stations in a mobile radio network, it becomes possible to determine the location of any mobile station moving at some point in the mobile radio network with a much higher accuracy than has been possible in the prior art. This requires in addition that those mobile stations whose positions are to be calculated determine timing information of signals received from the plurality of base transceiver stations. Furthermore, since the knowledge of the timing differences allows to operate the base transceiver stations in a pseudo-synchronous manner, the way of effecting handovers of the mobile stations can be improved.
Advantageous embodiments of the present invention are defined in the subclaims.
The preferred embodiments of the present invention will be described in detail hereinbelow by way of example with reference to the accompanying drawings.